Field of the Invention
The present invention relates to a linear actuator utilizing a so-called piezoelectric characteristic.
As the linear actuator utilizing the piezoelectric characteristic, an actuator shown for example in FIG. 4 has been proposed.
This actuator has an excitation system including an excitation circuit 2, a piezoelectric member 4 and a resonance element 6, and a damping system including a damping circuit 8, a piezoelectric member 10 and a resonance element 12. Oscillation produced in the vertical direction X in the drawing from the piezoelectric member 4 by the excitation circuit 2 is amplified by means of the resonance element (horn) 6 to thereby excite one end of a rod 16 for moving an article to be carried 14. Oscillation thus produced is damped by means of the damping system located on the other side. Therefore there occurs a specific carrier wave on the rod 16 to move the article 14 from the damping system side toward the exciting system side.
However, since the linear actuator utilizing such a conventional piezoelectric characteristic uses plate-like piezoelectric members 4 and 10 as oscillation sources, a great voltage must be applied to the piezoelectric members 4 and 10 in order to obtain a great oscillation displacement usable for the actuator, and accordingly there is such a problem that a large-sized excitation system or a damping system will be required.
Also, since it was necessary to constitute the resonance system by combining the resonance members 6 and 12 produced of a metal and the piezoelectric members 4 and 10, there were problems such as limited shape, low mass producibility, and poor controllability.
Since the amount of distortion (amount of extension and contraction) is proportional to the strength of the electric field, the amount of distortion can be increased by decreasing the thickness of these members. Usually, however, these piezoelectric members 4 and 10, being difficult to decrease in thickness through processing, are unsuitable for mass production.